Many computer systems today are being equipped with expansion cards. Some cards contain a graphics processing unit (GPU) that is used primarily for 3-D applications, creating lighting effects and transforming objects each time a 3D scene is redrawn. The GPU is a single-chip processor that is capable of performing these mathematically intensive tasks and, thus, removing the burden of these calculations from the CPU. The GPU can perform billions of calculations per second, processing a minimum of ten million polygons per second and having over 22 million transistors.
The GPU generates a very large amount of heat that needs to be removed. In order to remove the heat, a blower structure, containing a cooling fan and ducting, and a heat sink are employed. Fans typically vibrate due to mass imbalance in their rotors. Such vibration is readily transmitted to air via a surface, such as a rigid fan-housing, causing sound to be produced. The cooling fan in the blower structure of a typical GPU card runs fairly quietly at low speed when not in a 3-D mode. However, when an application that is running enters a 3-D mode, the fan switches to full speed. At full speed, the noise level increases, remarkably, to around 45 decibels or higher. This noise level has been cited to be an irritation to users.
Prior Art FIG. 1 illustrates a typical configuration of a conventional heat removal system used to remove heat generated by a GPU. GPU 150, according to one embodiment of the conventional art, resides beneath a copper plate heat sink 140. Fan 110 is mounted on top of heat sink 140 with a portion of its impeller overlapping the GPU. Fan 110 is contained in a housing that forms a duct 120 for directing the air from fan 110 over heat sink 160. Together, fan 110, its housing and duct 120, comprise the blower structure that is mounted on top of the GPU. Heat sink 160 is a copper heat sink, having a series of fins. There is a second housing 130 that forms an a duct for directing ambient air that enters through intake openings 170 in mounting bracket 190 and enters fan 110 over the top of the fan motor for aiding in the removal of heat generated by GPU 150. The air passing over heat sink 160 is exhausted through an opening 180 in bracket 190.
Duct 120 of Prior Art FIG. 1 has an acoustical effect. Its design causes sound waves that are generated within the duct by the fan and fan motor to be amplified. Any additional vibrations and/or noise, such as those from the fan motor that is slightly off balance or from electrical noise, will contribute further to the sound that is generated. The large amount of sound (45 to 50 db), that is observed to be generated when fan 110 runs at high speed, creates an annoyance for many users.
Another problem with the card configuration of FIG. 1 is that having the fan structure mounted on top of the GPU and the heat sink mounted on top of the fan structure creates a thick design. Often the GPU card takes up two or more slots on the computer system due to the thickness of the design.
In addition to the noise produced, there is an additional problem with the GPU card with regard to its flexibility. The GPU chip is fairly fragile, in that it contains balls that are easily broken away if the chip is flexed. The card has exhibited a flexibility, when dropped, which allows the GPU chip to break. Both the noise factor and the GPU chip breakage due to flexing of the card present undesirable features of the conventional GPU card.